Pharmacognosy Alkaloids

lec 8

Sometimes called alkaloids, xanthine derivatives are stimulants and bronchodilators. Caffeine 1,3,7-trimethyl

xanthine is the most common and found in tea and coffee. The derivative theophylline (1,3-

dimethylxanthine, found in trace amounts in tea) is used in the treatment of asthma.

Theobromine (3,7-dimethyl-xanthine) is found in chocolate – which is made from the beans of Theobroma

cacao (NB: ‘Theobroma’ means food of the gods!)

Purine alkaloids

Caffeine

Occurs in

Coffee ,tea , cacao, cola and mate. Although can be produce synthetically , but usually prepared from tea. Solubility in water can be markedly increased by the presence of citric acid or benzoic acid , medicinal compounds of this class are

citrated caffeine which is suitable for intramuscular injection

To treat circulatory failure

Caffeine and related derivatives are CNS stimulant.

Green tea is prepared in China and Japan

By rapidly drying the fresh leaves in copper pans over a mild

artificial heat.

Black tea the fresh leaves are left until fermentation began.

Lupinane alkaloid

Quinolizidine

The most important alkaloid is Sparteine is a class of antiarrythmic agent a sodium channel blocker. It is

an alkaloid and can be extracted from scoparius broom. It is the predominant alkaloid in Lupinus mutabilis, and is thought to chelate the bivalents

calcium and magnesium It is not FDA approved for human use as an antiarrhythmic agent, and it is not

included in. is used as oxytocic (stimulate contraction of uterus

It is also used as a chiral base in Organic synthesis

Biosynthesis of sparteine

Note: designate the type of reaction in each step

Veratrum album (the white veratrum) grown in europe used as pesticide

Verartrum viridi (green veratrum) contains the alkaloid

veratraine and protoveratrine

Veriloid is a mixture of veratrum alkaloid.Used as hypotensive agent.

Pseudoalkaloids 1- Steroidal alkaloids

Verartrum toxicity

Veratrum species produce highly toxic steroidal alkaloids only when the plants are in active growth. During the winter months, when the plant enters its dormant stage, it degrades and metabolizes most of its toxic alkaloids. Herbalists and Native Americans who used this plant for medicinal purposes harvested the roots during the winter months when the levels of toxic constituents were at their lowest.

The roots of V. nigrum and V. schindleri have been used in Chinese herbalist (where plants of this genus are known as "li lu Li lu is used internally as a powerful emetic of last resort, and topically to kill external parasites, treat tinea and stop itching.. Some herbalists refuse to prescribe li lu internally, citing the extreme difficulty in preparing a safe and effective dosage

Solanum alkaloids A good number of plants belonging to the natural order Solanaceae have been found to accumulate favourably several steroidal alkaloids based on a C27 cholestane skeleton, such as: solasodine,

solanidine

Solanum alkaloids

Terpenoid alkaloids Aconite: Is the dried roots of Aconitum napellus (Ranunculaceae). Aconite contains diterpine alkaloids aconine and aconitine. Aconine

antineuralegic liniment a “counterirritant” for treating facial pain, joint pain Aconite root contains chemicals that may improve circulation, but it also contains chemicals that can seriously harm the heart, muscles, and nerves.

Pseudo alkaloids

Aconitine is ester of aconine

Used to treat neuralgia and induce arrhythmia in experimental animal

Biosynthesis of aconite alkaloids

THE END

Thank you for listining